The present invention relates to rotary or disc mowers of a type including an elongate cutterbar, and more particularly relates to such a cutterbar constructed of a plurality of modules secured together in end-to-end relationship with one another.
On rotary mowers, the space available for the transmission of power to each cutting unit is very shallow. This is because the drive is below the cutting units which are kept as close and flat to the ground as possible for close cutting. Two types of cutting unit drives predominate, these being a cross-shaft drive with bevel gears and a spur gear drive. The spur gear drive is preferred since spur gears can be placed in a flat arrangement which makes it easier to achieve close cutting.
Known spur gear drive trains normally include either a plurality of series-arranged gears, some being idler gears and others being cutting unit drive pinions, or a plurality of series-arranged idler gears having drive pinions arranged parallel thereto and respectively meshed with respective ones thereof in accordance with the desired direction of rotation of a respective cutting unit.
U.S. Pat. No. 4,693,061 discloses a one-piece cutterbar defining a gear housing containing a spur gear drive train and featuring a structure for removably mounting each of the idler gears within the housing. This featured structure includes a first member having a cylindrical shank inserted through axially aligned holes machined in the top and bottom of the housing and having an enlarged head sealed against an outer top surface of the housing. A second member is received in a cylindrical cavity formed in the lower end of the shank of the first member and includes an enlarged head defining an annular groove receiving the lower end of the shank. A coupling bolt extends through an aperture in the first member and is threaded into the second member to thereby hold the first and second members together. A bearing is mounted to the center of an idler gear and is received on the shank of the first member.
This above-described idler gear mounting structure is not entirely satisfactory since the first and second members are specially shaped parts and since a total of three seals must be used to prevent lubrication fluid from leaking from the gear housing.